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Brookfield AMETEK

Grated Cheese

Powder Flow Application Data Sheet

USE

Cheese used in recipes, toppings, etc.

Test Equipment

  • Instrument: Powder Flow Tester (PFT)
  • Trough: 230 cc, 6-inch diameter
  • Lid Type: Vane Lid, 304 s/s, 33cc, 6-inch diameter (Flow Function)
    Wall Lid, 304 s/s, 2B finish, 6-inch diameter (Wall Friction)
  • Type of Test: Flow Function Test, Wall Friction Test
  • Temperature: Room Temperature (70-72° F)
  • Humidity: 48%

Method

A Brookfield Powder Flow Tester, equipped with Powder Flow Pro software for automated instrument control and data acquisition, was used to test this name brand corn starch. The corn starch was scooped into the trough, and the scraping tool was then used to evenly distribute the powder throughout the trough. After recording the sample weight and entering it into the software, a standard flow function test and then a wall friction test were run. Time required for each test was 35 minutes and 20 minutes respectively.

Parameters Measured

  • Flowability: Very Cohesive to easy flowing
  • Wall Friction: 45 to 25
  • Bulk Density: 525 kg/m (fill density) to 750 kg/m

Analysis

  • Hopper Shape: Conical
  • Arching Flow Factor: 1.40
  • Critical Arching Dimension: 54.9 mm (2.16 inches)
  • Rathole Diameter: Dependent on bin diameter

Results


Figure 1: Grated Cheese Flow Function Graph

Figure 1 shows the flowability of the grated parmesan cheese at different levels of consolidating stress. These results show that the grated parmesan cheese is cohesive throughout all the levels of consolidating stress.

Note: The Flow Function data is indicated by the red line. The other lines are references (or "Standard Flow Indices"), which distinguish the different types of flow behavior, ranging from "non-flowing" to "free flowing".


Figure 2: Grated Cheese Wall Friction Graph

Figure 2 represents the angles of wall friction at different levels of normal stress. Angles of wall friction represent the friction between the sliding powder and the wall of the hopper or chute at the onset of flow. In this test a stainless steel lid was used, illustrating what the friction would be like if the grated parmesan cheese was in a stainless steel hopper. At a low normal stress of about .5 kPa, the effective angle of wall friction is about 45 and goes down to about 25 at higher levels of normal stress (4.75 kPa). Wall friction angles above 30 are considered very high and angles below 10 are considered very minimal.


Figure 3: Grated Cheese Bulk Density Graph

Figure 3 shows the bulk density of the material at different levels of consolidating stress. This graph tells us that the grated parmesan cheese has a fill density of about 525 kg/m and rises to about 750 kg/m at around 12.5 kPa of consolidating stress. In general, a free flowing powder will show very small changes in bulk density, while a cohesive or poor flowing powder will generally show a large increase in bulk density.

Conclusion

The grated parmesan cheese is a cohesive powder throughout all consolidation stress levels. The grated cheese has high amounts of wall friction against stainless steel. At the lower consolidation levels wall friction is extremely high (30 to 45) and may prevent reliable flow as the hopper empties. Other possible problems include arching (when the powder forms a cohesive bridge over the outlet) and ratholing (when the powder flows out only from the center leaving the rest of the material static against the walls). The critical arching dimension, of 2.16 inches (54.9mm) provides a conservative estimate to prevent arching from happening, provided the minimum outlet dimension of the hopper exceeds this value. The critical ratholing dimension is dependent on the diameter of the bin. The rathole diameter can be automatically calculated by Powder Flow Pro once the bin diameter is entered.